The correct answer is C. L.
The missing character is the letter that is in the middle of the alphabet. The letters in the alphabet are A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, Y, and Z. The letter in the middle of the alphabet is L.
The other options are incorrect because they are not in the middle of the alphabet. The letter A is the first letter of the alphabet, the letter B is the second letter of the alphabet, the letter C is the third letter of the alphabet, and so on. The letter R is the 18th letter of the alphabet, and the letter F is the 6th letter of the alphabet.